How to achieve at least a tenfold increase in supply of geothermal power and heat

A report launched today by the International Energy Agency (IEA) shows that there is potential to achieve at least a tenfold increase in the global production of heat and electricity from geothermal energy – heat emitted from within the earth’s crust – between now and 2050.

Renewable sources of energy such as wind, solar and geothermal will have to comprise a much greater share of the global energy mix in the coming years if the level of carbon dioxide in the atmosphere is to be kept below 450 parts per million – a key threshold in limiting global temperature increase to 2°C, which leaders agreed to at the UN climate change talks in Cancun in 2010.

The IEA report says that through a combination of actions that encourage the development of untapped geothermal resources and new technologies, geothermal energy can account for around 3.5% of annual global electricity production and 3.9% of energy for heat (excluding ground source heat pumps which the report did not consider) by 2050 – a substantial increase from current levels of 0.3% and 0.2%, respectively.

“This would be an important contribution to global efforts of reducing carbon emissions, using a reliable source of energy that is available all over the world, every day of the year, as it does not fluctuate with the weather or season,” said IEA Executive Director Nobuo Tanaka, who launched the report, Technology Roadmap:Geothermal heat and power, at the EURELECTRIC annual conference in Stockholm.

The report is the latest in the IEA series of technology roadmaps, which aim to guide governments and industry on the actions and milestones needed to achieve the potential for a full range of clean energy technologies.

Untapped areas, emerging technologies

Although active geothermal exploitation has been in use for more than a century, to date, efforts to extract geothermal energy have concentrated on areas with naturally occurring water or steam, often found in volcanic areas.

However, Milou Beerepoot, the report’s author and a senior analyst at the IEA, noted that a large share of such ‘low hanging fruit’ remains unexploited in developing and emerging economies. Ms. Beerepoot said that efforts should be expanded to solve economic and non-economic barriers that hinder further exploitation in these countries.

Moreover, she observed that geothermal energy can also be extracted from many deep aquifer systems, of which there are many all over the world. These resources can typically be reached at a depth of 3 kilometres and produce temperatures in excess of 60ºC. Use of these aquifers is expected to grow quickly, reflecting their wide availability and increasing interest in their use for both heat and power.

In addition to these untapped areas, the vast majority of the world’s geothermal energy within drilling reach – which can be up to 5 kilometres – is found in rock that is relatively dry and impermeable. These areas, which are found all over the world and contain insufficient water for natural exploration, are known as hot rock resources.

Currently, technologies that allow energy to be tapped from hot rock resources – the best known is enhanced geothermal systems (EGS) – are still in demonstration stage, but the IEA report suggests that governments should provide sustained and substantially high research, development and demonstration resources to plan and develop at least 50 EGS pilot plants during the next decade.

With these systems, a well is drilled deep into the ground, typically below 1.5 kilometres. Water is then injected into the well at sufficient pressure so as to create fractures in the rock. Other wells are then drilled in order to pump up the water, which has been heated by the hot rocks. “If these enhanced geothermal systems are developed further, this will significantly open up global exploitation of geothermal resources,” said Ms. Beerepoot.

Incentive schemes, permits and databases

Key areas of action for governments identified in the report are the establishment of targets and economic incentive schemes for mature and nearly mature technologies as well as for advanced technologies that are not yet commercially viable. Another proposed area of action outlined in the report focuses on the need for streamlined and time-effective permit procedures, which are necessary for all new geothermal plants.

In addition, the report stresses that publicly available databases, protocols and tools should be developed, which could be used to assess, access and exploit geothermal resources and thereby accelerate its development. “[This] requires co-operation among geothermal and hydrocarbon industry groupings, national authorities and research institutes,” wrote Ms. Beerepoot.

The risk of finding insufficient temperatures or flow rates can be addressed by more competitive and advanced drilling technologies as well as advanced resource and assessment technology. Financial instruments such as risk guarantee schemes can also reduce geothermal development costs.